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is essential that the blade is kept flat to the stone's surface and well-controlled circular strokes used. The two faces of the blade may have to be dealt with several times in this way before the wire edge is finally obliterated.
After the old oil and abrasive have been carefully cleaned from the blade, the final sharpening is carried out in a similar manner on an Arkansas or other stone of hard texture. As before, the blade is reversed after a few strokes have been made and its back is carefully honed to remove any part of the fine edge that has been turned backwards.
Usually, the weight of the jig alone will suffice for the final stage of the stoning, and at the same time, any remnant of the wire edge remaining from the previous honing will quickly disappear, leaving a fine, sharp, smooth cutting edge.
The sharpness of this edge can be tested either against the skin of the ball of the thumb, or on the hairs on the
back of the wrist ; when the blade under light pressure catches into the skin, or cuts the hairs cleanly, its sharpness is well demonstrated.
It should be noted that the corners of the blade should be formed to a small radius, as illustrated in Fig. 73, in order to prevent the sharp corners from marking the work when the plane is in use. The rounding of the corners is carried out by rocking the roller rest towards either corner at the end of the stroke as the blade is moved along the stone,
The alternative form of commercially-made roller rest, illustrated in Fig 9, Chapter II, has a roller-guide which runs on the bench and not on the stone, but it will be apparent that its greater bulk renders it generally less handy, and rather cumbersome when the back of the blade is honed while the jig is still attached.
Grinding the Iron. If the cutting edge of the blade becomes nicked, small notches can be removed on a coarse carborundum stone, but where the damage is greater, regrinding will be necessary. Again, when the original ground bevel has been largely obliterated by honing, the form of the edge should be restored by grinding the blade.
If only a wheel of small diameter is available, the side of the wheel must be used, as, otherwise, the deep hollow-grinding resulting from the use of the periphery of the wheel would seriously weaken the cutting edge.
In any case, when grinding the blade with a carborundum wheel, great care must be taken to avoid overheating and softening the end portion of the iron.
In order to maintain the correct angle and to hold the blade securely, it is essential to employ a simple jig of the type illustrated in Fig. 74. This appliance consists of a wooden block to rest on the grinding table, and a metal strap with clamping screws to hold 'the blade in place.
It will be appreciated that the angle at the upper surface of the block must be adjusted to conform with the diameter of the grinding wheel, and also with the height of the work above the centre line, as determined by the setting of the rest. The actual sharpening operation is carried out by passing the plane-iron backwards and forwards across the face of the wheel.
The Router Plane. As shown in Figs. 75 and 76, this plane has a cutter ground to form a chisel edge at its lower end.
In the example illustrated in the drawings the cutter was made by the writers from a length of square-section tool steel, but those supplied commercially are usually of hexagon form and fit into a groove machined in the tool post.
As the router is generally employed to cut across the
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